Cooling fan modules are used to cool the engine in motor vehicles. The general aim is to manufacture such cooling fan modules as economically as possible. The comfort of the vehicle occupants is also a further aspect, especially with regard to minimising the noise generated by the cooling fan module.
A cooling fan module typically consists of a fan impeller, in which a motor to drive the fan impeller is located, and a frame which comprises assembly struts for fixing the fan impeller. The fan impeller of a cooling fan module is designed to produce an air flow with which the heat generated by the engine is to be removed. The cooling fan modules used at present have what is known as a gap flow in addition to the main flow. The gap flow refers to the flow which forms between the fan impeller and the frame due to negative pressure and which tends to swirl due to the rotation of the fan impeller. The swirling gap flow works against the main flow, leading to a negative impact on the flow behaviour of the cooling fan module. This defective flow sometimes leads to a very high level of noise being generated, reducing the comfort of the passengers during vehicle operation.
DE 10 2008 046 508 A1 describes a fan device for ventilating a combustion engine for a motor vehicle having at least one fan impeller with fan impeller blades for air intake, said blades connecting at least one fan impeller casing to a fan impeller hub, having at least one fan frame in which at least one fan impeller is located, a first gap being formed between at least one fan impeller casing section and one fan frame section such that it runs radially, at least in part, with respect to a main air flow direction and in the direction of the centrifugal force arising when the fan impeller is moved in rotation, in order to minimise at least one air flow.
DE 10 2007 036 304 A1 describes a device for cooling an engine, comprising a heat exchanger through which air can flow, a fan located in the region of the heat exchanger having a fan shaft, and a fan cowl located on the heat exchanger, said fan cowl surrounding a flow chamber between the fan and the heat exchanger and being delimited by an outer chamber, a gap through which air can flow being provided in the region of a radial outer circumference of the fan by means of the fan cowl, a gap flow from the flow chamber being able to flow through said gap into the outer chamber, causing the gap flow to flow into the outer chamber in a different radial direction to the fan shaft.